210 NITROGEN BODIES OF MODERN CHEMISTRY. 



in cold water, often changed; for tlte acid must be ice-cold to insure 

 success. In this perfectly cold mixture immerse now, flake by flake, 

 strand by strand, the cellulose, the pure vegetable tibrin. The purer 

 the liltriu the drier and the freer from all mechanical soiling, the better 

 of course will l)e the result. The cotton is immersed in the liquid by 

 pressing it down with a glass rod; we wait till all the air-bubbles escape, 

 till the cotton is fully saturated with the acid ; moreover, we are careful 

 to immerse no more cotton than can be contained without pressure and 

 will be entirely covered by the acid. Half an hour, as Ihaverepeatedly 

 satistied myself, is sufficient for the process ; still there is no harm in 

 leaving the cotton in the acid for an hour or several hours; thirtj^ or 

 forty minutes, however, are amply sufScient for the required effect. 

 This done, with the glass rod take out the wet cotton, press it between 

 thick plates of glass to remove the superfluous acid, throw it into an 

 abundance of cold water to reduce the temperature, and immediately 

 pick it apart, for if you let the compressed cotton fall into the water and 

 lie there in a mass, you will find that, with a perceptible increase of 

 temperature and the escape of reddish brown vapor, it gradually dis- 

 solves and disappears. After the cotton is thus pulled apart, and, as it 

 were, drowned and quenched in cold water, it must be carefully washed, 

 in a runniug stream if possible, for you will accomplish as much in six 

 hours with runniug water, v.iiich easily penetrates among the fibers, as 

 in two or three days with standing water. If all has been done as 

 directed, you have first-class gun-cotton. It has now only to be dried, 

 in a temperature not exceeding 100°, to expel all the Avater, and then'it 

 may be kept for years withcfiit the slighest deterioration. 



We know^ what wonderful changes of opinion have taken place in our own 

 time in respect to gun-cotton. The Austrian minister of war has really 

 played with it the poetical game of the daisy ' " Thou lovest me well, 

 through good and ill, a little, or not at all." A large amount of money was 

 exj)ended on gun-cotton. At first, it was glorified ; later, doubts were 

 entertained ; and then, when suddenly the tower of Simmering flew into 

 the air, gun-cotton fell into disrepute. And yet England has recently 

 made it the subject of a thorough investigation, and opinions in regard 

 to it now seem very favorable. I have here some gun-cotton in the form 

 of skeins and lamp-wick. This specimen is fully eleven years old, and 

 in that time has not changed in the least, absolutely not in the least. 

 It ?s just as eiiective to-day as when first made. It is a property of gun- 

 cotton that in a moist condition, and notably when it has been imperfectly 

 washed, it is decomposed in a way which may result in a partial dissolutiou 

 and eventually in explosion. A spontaneous conbustion of clean, well 

 washed and dried gun-cotton is inexplicable on scientific principles and is 

 not known to have occurred. On being ignited gun-cotton explodes with- 

 out smoke or vapor, and with no residue of ashes. ^Ve i^erceive oidy a 

 weak odor of nitrous acid. It is a great advantage in the use of gun- 

 cotton in blasting, that it does not leave that stifling atmosphere, that 



